Motor vehicle, especially passenger motor vehicle

ABSTRACT

In a motor vehicle, especially in passenger motor vehicles, its vehicle floor is constructed in the rear area rising toward the vehicle end for achieving a good traction of the vehicle; an air foil with an air foil profile is arranged in the rear diffusor formed thereby at a distance from the road surface that corresponds to the distance of the vehicle body in front of the vehicle rear section of the vehicle so that a negative lift becomes effective at the air foil with an in-flow of air coming from the vehicle front section.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a motor vehicle, especially to apassenger motor vehicle in which for purposes of achieving road tractionof the vehicle, the vehicle floor in the rear area is constructedessentially smooth-surfaced and rising toward the vehicle end and an airfoil is arranged in the space underneath the rising rear floor, where anegative lift becomes effective with an incident flow coming from thevehicle front section.

In a known motor vehicle of this type which is constructed as passengermotor vehicle, the vehicle floor is bent upwardly shortly before itsrear end and the air foil which in plan view has the shape of a sectionof a circle whose circular arc forms the front edge of the air foil, isarranged underneath the horizontal vehicle floor located in front of thebending place and of the rising rear floor in such a manner that itadjoins with its rear, upwardly directed end the inclined surface formedby the rising rear floor so that the inflowing air is conducted towardboth vehicle sides (French Patent No. 1,529,933).

In another known passenger motor vehicle (U.S. Pat. No. 4,379,582,JP-GM-OS Sho No. 55-117369), a rear bumper unit is provided whichincludes a main bumper secured at the vehicle body and a further bumperwhich is arranged underneath the main bumper while leaving free aninclined rearwardly rising air opening, and which is secured at the mainbumper. The further bumper as also its mountings consist ofshock-absorbing elastic material, is constructed as air foil withinverted air foil profile and with its forward end protrudes over theforward area of the main bumper forwardly underneath the rear end of therear section of the vehicle body.

A further passenger motor vehicle with an air foil having an air foilprofile which is arranged underneath the rear area of the vehicle bodyand guides inflowing air coming from the front obliquely rearwardly, isdisclosed in the JP-GM-OS Sho No. 52-63828.

The known air foils are always arranged only in the rear area. They actessentially as air guide devices.

The present invention is concerned in the first instance with the taskto provide a motor vehicle of the aforementioned type which is suitablefor the practical use in the usual road traffic and has an aerodynamicconfiguration which assures a good road traction, especially also athigh driving velocities.

The underlying problems are solved according to the present invention inthat the forward end of the rising rear floor is arranged at leastapproximately within the area of the vehicle rear axle, in that therising rear floor forms the top side of a rear diffusor whose bottomside is formed by the road surface, and at the vehicle end has aconsiderable spacing from the vehicle-tire contact surface (roadsurface), and in that the air foil is so arranged that it protrudes withits forward end into the space between the vehicle rear wheels and itsbottom side has at least the same distance from the vehicle tire contactsurface as the vehicle floor at its lowest place in the vehicle areaslocated in front of the vehicle rear section. It is achieved therebythat a considerable negative lift dependent on driving velocity isproduced at the vehicle rear section with simple means without adeviation of the external configuration of the vehicle from the usualconfiguration in a disturbing manner, which configuration is fixedfar-reachingly by legal rules and regulations and by practicalrequirements. The present invention is advantageous in particular forsmaller and more light-weight vehicles, especially for sportytwo-seaters. It enables not only a good traction but also the productionof high lateral guide forces and therewith a good tracking and drivingstability. It can be used in vehicles with different types of drive, forexample, in vehicles with a standard drive, i.e., with a forwardlyarranged engine and a rear wheel drive, in vehicles with front engineand front wheel drive or in those with four wheel drive.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the presentinvention will become more apparent from the following description whentaken in connection with the accompanying drawing which shows, forpurposes of illustration only, several embodiments in accordance withthe present invention, and wherein:

FIG. 1 is a partial schematic side elevational view of a firstembodiment of a passenger motor vehicle in accordance with the presentinvention, illustrated in part in cross section;

FIG. 2 is a partial bottom plan view of the passenger motor vehicleaccording to FIG. 1;

FIG. 3 is a schematic longitudinal cross-sectional view through the rearpart of a second embodiment of a passenger motor vehicle in accordancewith the present invention;

FIG. 4 is a schematic view, similar to FIG. 3, illustrating thegeometric coordination in the passenger motor vehicle of FIG. 3;

FIG. 5 is a schematic view illustrating the air flow in the passengermotor vehicle according to FIG. 3, indicated by flow lines;

FIG. 6 is a schematic view illustrating the pressure distribution causedby the air flow and pressures and forces caused thereby at the passengermotor vehicle according to FIG. 3;

FIG. 7 is a schematic longitudinal cross-sectional view through a partof the rear section of a third embodiment of a passenger motor vehiclein accordance with the present invention;

FIG. 8 is a schematic longitudinal cross-sectional view through a partof the rear section of a fourth embodiment of a passenger motor vehiclein accordance with the present invention;

FIGS. 9 to 11 are schematic longitudinal cross-sectcional views of apart of the rear section of a fifth embodiment of a passenger motorvehicle illustrating the vehicle under different load conditions;

FIG. 12 is a schematic longitudinal cross-sectional view through therear section of a sixth embodiment of a passenger motor vehicle inaccordance with the present invention;

FIG. 13 is a schematic bottom plan view of the passenger motor vehicleaccording to FIG. 12:

FIG. 14 is a schematic longitudinal cross-sectional view through a partof the rear section of a seventh embodiment of a passenger motor vehiclein accordance with the present invention;

FIGS. 15 to 19 are schematic views of several embodiments of turbulencegenerators for use with the present invention;

FIG. 20 is a schematic longitudinal cross-sectional view through a partof the rear section of an eighth embodiment of a passenger motor vehiclein accordance with the present invention;

FIG. 21 is a schematic perspective and partly cross-sectional view of apart of the air foil according to FIG. 20;

FIG. 22 is a cross-sectional view taken along line 22--22 of FIG. 21;

FIGS. 23 and 24 are schematic longitudinal cross-sectional views througha part of the rear section of ninth embodiment of a passenger motorvehicle in accordance with the present invention in different positionsthereof; and

FIGS. 25 and 26 are schematic longitudinal cross-sectional views througha part of the rear section of a tenth embodiment of a passenger motorvehicle in accordance with the present invention, again in differentpositions.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to the drawing wherein like reference numerals are usedthroughout the various views to designate like parts, the firstpassenger motor vehicle according to FIGS. 1 and 2 is constructed assporty two-seater vehicle. It includes two vehicle axles with twovehicle wheels each. The vehicle engine 1 is arranged in front, thevehicle drive takes place by way of the vehicle rear wheels 2. Thepassenger motor vehicle has a far-reachingly aerodynamically favorableconfiguration. In order to achieve an in-flow of the air reachingunderneath the vehicle which is as undisturbed as possible, arounded-off venturi front apron 3 is provided. The latter can be securedat the vehicle body with a large road clearance, elastically with lesserroad clearance or, regulated or controlled, for example, in dependenceon the driving velocity or on the load of the vehicle with a variableroad clearance. It may produce an aerodynamic negative lift. Forachieving a favorable vehicle underflow, a far-reachinglysmooth-surfaced lower covering 4 is provided for the engine andtransmission space adjoining the rear end of the venturi front sectionapron 3. The outlet openings for the engine cooling air are so arrangedthat a disturbance of the underflow by the exiting cooling air isfar-reachingly avoided. Adjoining the rear end of the lower covering 4and the lateral ends thereof an also far-reachingly smooth-surfacedcentral floor 6 is arranged on both sides of the exhaust system 5 whichextends approximately in the vehicle longitudinal center plane; thecentral floor 6 has a slight concave curvature toward the vehicleinterior for the production of a vacuum and ahead of the area of therear axle suspension is spaced with its area near the ground atapproximately the same distance from the road surface 7 forming thevehicle tire contact surface as the lower covering 4. In lieu of thearched or curved construction of the central floor 6, a flat centralfloor may also be provided. In order to prevent far-reachingly anexchange flow between the vehicle underflow and the lateral vehiclecircumcirculations, downwardly projecting threshold aprons 8 arearranged at the vehicle sides which have as small a ground clearance aspossible. The exhaust installation 5 is so constructed with exhaustlines, mufflers, catalyst and fire protection covering that thevehicle-underflow remains far-reachingly undisturbed. The structuralparts of the rear suspension 9 are covered off within the area of thepivotal connections and are constructed aerodynamically favorably byconfiguration or by covering parts. Also the rear axle transmissionhousing 10 is aerodynamically constructed within the area of its coolingribs.

The central floor 6 passes over at its rear end within the area in frontof the rear axle suspension into a rear floor 11 which rises from itsfront end toward the vehicle rear end and is constructed essentiallysmooth-surfaced. The transition between the central floor 6 and the rearfloor 11 takes place gradually and is constructed well rounded-off foravoiding flow detachments. The rear floor 11 forms the top side of arear diffusor 12 whose bottom side is formed by the road surface 7. Therear diffusor 12 can be constructed as venturi nozzle. To the rear ofthe transition area in which the rear floor 11 adjoins the central floor6, the rear floor 11 is constructed far-reachingly plane or flat and hasa constant slope. The rear end of the rear floor 11 adjoins the lowerend of the rear terminal wall 13 which is arranged approximatelyvertically. The rear end of the rear floor 11 thereby has a groundclearance that is approximately four times as large as the groundclearance of the central floor 6 in the rear area thereof. The groundclearance of the rear end of the rear floor 11 is furthermoreapproximately as large as the diameter of the vehicle rear wheels 2.

An air foil 14 is arranged in the space underneath the rear floor 11which has such a cross section that a vacuum and therewith a negativelift is produced at its bottom side in case of incident flow from thevehicle front section (inverted air foil profile). The air foil 14serves additionally as air guide device for the air which flows throughthe channel between the bottom side of the rear floor 11 and the topside of the air foil 14, whereby a pressure and therewith a negativelift also acts on the same. The air foil 14 has an approximatelyrectangular configuration in vertical projection (FIG. 2). It isarranged at such a height above the road surface 7 that its bottom sideat its lowest place has at least the same ground clearance as thecentral floor 6 in its rear area. The lower covering 4 underneath thevehicle engine 1 also has approximately the same ground clearance. Withits forward end, the air foil 14 protrudes into the space between thetwo vehicle rear wheels 2, and more particularly approximately with itsforward third part. With front-wheel-drive variations, the air foil canbe extended approximately up to the front edge of the rear wheel.

The rear bumper 15 is arranged with a gap spacing to the rear of the airfoil 14; the location of the bumper 15 at the vehicle is determined byrules and regulations. The rear bumper 15 thereby forms with its partthat is arranged to the rear of the air foil 14, a continuation of theair guide device. It is located with a spacing underneath the rear endof the rear floor 11 and is secured by means of lateral arms 16 at thevehicle body, at which is also secured the air foil 14 by means ofstruts (not shown).

In the vehicle according to the present invention, a far-reachinglyundisturbed flow is achieved in the underfloor area essentially over theentire vehicle length. This enables a good traction. The rear diffusor12 and the air guide device which is formed by the air foil 14 and therear bumper 15 are so matched to one another that the flow into the reardiffusor and the flow out of the rear diffusor take place undisturbedand as great as possible an amount of negative lift is supplied at therelatively light-weight rear end of the vehicle. It is thereby takeninto consideration that the ground clearance of the vehicle body isvariable in dependence on the load of the vehicle and the respectivedriving conditions and the floor contour in the transition area betweenthe central floor 6 and the rear floor 11 and the outflow tangent ofthis transition area are to be designed for an optimum flow with respectto the air foil 14 so that notwithstanding a differing inflow, thefunction of the rear diffusor 12 and of the air foil 14 is alwaysassured also in case of extreme positions of the vehicle body. In orderto achieve a height position of the vehicle body which remains the sameas much as possible and additionally is as low as possible, it may beadvantageous to utilize a level regulation at least at the rear axle.

The second passenger motor vehicle according to FIGS. 3 to 6 differsfrom the first passenger motor vehicle according to FIGS. 1 and 2especially by the rear area of the rear floor and the configuration ofthe air foil and of the rear bumper.

According to FIGS. 3 to 6, the rear floor 17 is not constructed flat inits rear area but is constructed slightly convexly curved so that arounded-off diffusor termination 18 is formed. The rear end of the rearfloor 17 adjoins the lower end of the rear terminal wall 19 which in itslower area is constructed slightly concavely curved so that a sharp(detachment) edge 20 is formed at the rear end of the rear floor 17. Thetransition between the rear terminal wall 19 and the upper wall 21 ofthe vehicle rear section 22 is constructed as rear spoiler 23. Withinthe area of the vehicle rear axle (not shown) the rear floor 17 is drawnupwardly over at least a part of the vehicle width in order to createspace for the movable drive parts of the drive unit of a driven rearaxle. The rear diffusor 24 exhibits within this area a disturbance owingto the recess 25, however, is not significantly impaired thereby in itsoverall function. With a front wheel drive vehicle, the rear floor,deviating therefrom, may extend uniformly and uninterruptedly alsowithin the area of the non-driven vehicle rear wheels essentially overthe entire vehicle width above the vehicle rear axle as top side of therear diffusor from its forward area to its rear area. This is indicatedby a dash line 26.

At the forward end of the rear floor 17, where the latter passes overinto the central floor 6, the rear floor 17 has a spacing 27 (FIG. 4)from the road surface 7 which, however, is not constant but is variablein dependence on the load of the vehicle and the instantaneous drivingconditions. To the rear of the transition area between the central floor6 and the rear floor 17, the rear floor 17, which rises rearwardlyobliquely, has in its center area an essentially constant slope. Theangle of inclination α which is subtended by the center area of therising rear floor 17 and the horizontal amounts to about 25° but mayalso assume different values between approximately 10° and approximately40° in other realizations. In the rear area of the rear floor 17 inwhich the latter is curved convexly, the slope increases gradually. Thetangent at the rear end of the rear floor 17 subtends with thehorizontal an angle of inclination β of about 70°. This angle, however,may also assume different values, for example, between about 40° andabout 90° with different realizations. The rear end of the rear floor17, where a sharp detachment edge 20 (FIG. 3) is formed, has a spacing28 (FIG. 3) from the road surface 7 which is more than four times aslarge as the distance 27 of the forward end of the rear floor 17 fromthe road surface 7 and approximately as large as the diameter of thevehicle rear wheels 2.

An aerodynamic body is provided as air foil 29 whose front portion 30 isconstructed well-rounded-off to assure a detachment-freecircumcirculation of the air foil 29. The bottom side 31 of the air foil29 is curved convexly and forms the vacuum or suction side of the airfoil 29. The top side 32 of the air foil 29 is constructedfar-reachingly flat, but may also be constructed slightly convexly. Itforms the pressure side of the air foil 29. At the rear end of the airfoil 29, the top side 32 thereof has a flat concave recess 33 (FIG. 3).The rear end of the air foil 29 terminates approximately wedge-shaped.

The air foil 29 is arranged essentially flat. It rises slightly from infront toward the rear. The angle γ subtended by the front area of thetop side 32 of the air foil 29 with the horizontal amounts toapproximately 10°, but may also assume other values approximatelybetween 5° and approximately 30° with different realizations. The angleof attack is to be so selected that a maximum vacuum results at thebottom side 31 of the air foil 29. The bottom side 31 of the air foil 29has at its lowest place a spacing 34 from the road surface 7 which is atleast as large as the spacing 27 which the forward end of the rear floor17 has from the road surface 7 so that a touching-down of the air foil29 on the ground for reasons of inadequate road clearance is precluded.The air foil 29 is additionally arranged in such a manner that aboundary curb angle remains free above the road surface 7. The air foil29 protrudes approximately with its forward third into the space betweenthe two vehicle rear wheels 2. It is arranged underneath the rear halfof the center area of the rear floor 17. Its front edge liesapproximately underneath the rear end of the recess 25.

An auxiliary after-air foil 35 is connected in series with and to therear of the air foil 29 so that the air foil 29 acts as main air foil.The supporting component of the auxiliary air foil 35 is the rear bumper36 which has a bumper core 37 and is provided within the area to therear of the air foil 29 with an upwardly projecting tongue-like airguide extension 38 extending approximately over the width of the airfoil 29. The rear bumper 36 together with the air guide extension 38 isalso constructed as air foil profile in the area to the rear of the airfoil 29 in which it is component of the auxiliary air foil 35, so thatin case of an in-flow from the vehicle front section a negative liftbecomes effective also at the auxiliary air foil 35. The auxiliary airfoil 35 is arranged in an essentially steep manner. Its backside 39(FIG. 4) is constructed convexly curved. Its front side 40 isconstructed convexly curved in the lower area and concavely curved inthe upper area. The upper area of the auxiliary air foil 35 thereforehas an only slight tapering. It terminates essentially blunt. At therear end, the auxiliary air foil 35 is to be constructed as thin aspossible. A thickness of about 10 mm. to about 60 mm. is practicallyrealizable. The rear area of the auxiliary air foil 35 subtends with thehorizontal an exit angle ε of about 80°. This angle may assume optimumvalues between about 50° and about 90° with other realizations. Thelength of the auxiliary air foil 35 in the flow direction amounts toapproximately 80% of that of the air foil 29 but may also assumedifferent values, for example, between about 30% and about 80% of thelength of the air foil 29.

The auxiliary after-air foil 35 is arranged obliquely under and to therear of the rear area of the rear floor 17. Its forward end is locatedabove the rear end of the air foil 29. A through-flow gap 42 is presentbetween the rear end of the air foil 29 and the forward end of theauxiliary air foil 35 whose gap width 43 amounts to approximately 10 to60 mm. in the vertical direction. The bottom side 31 of the air foil 29and the backside 39 of the auxiliary air foil 35 form at leastapproximately a continuous curved configuration interrupted only by thegap 42. The rear area of the air foil 29 is so shaped that there is noflow detachment at the backside 39 of the auxiliary air foil 35. The airfoil 29 and the auxiliary air foil 35 act together as a gap-air foil inwhich the air flowing through the gap 42 enhances an attachment of theflow at the backside 39 of the auxiliary air foil 35. The distance ofthe air guide device formed by the air foil 29 and the auxiliary airfoil 35 from the rear floor 17 increases from a starting distance at theforward end of the air foil 29 toward the rear, reaches its maximumvalue approximately at the transition from the air foil 29 to theauxiliary air foil 35 and thereupon is again reduced toward the rearapproximately to the starting value. The rear area of the rear floor 17together with the front side of the auxiliary air foil 35 forms therebya nozzle 44 (FIG. 3) with an essentially upwardly and slightlyrearwardly directed outflow or exit direction. The outflow opening ofthe nozzle 44 can have an interior width 45 (FIG. 4) of about 30 mm. toabout 200 mm. between the rear area of the rear floor 17 and the frontside 40 of the auxiliary air foil 35.

The air, which flows from the vehicle front section underneath thevehicle rearwardly in a closed stream 46, is divided upon entry into therear diffusor 24 into two partial streams 47 and 48 (FIG. 5). The upperpartial stream 47 flows through the space between the rear floor 17 andthe top side 32 of the air foil 29 and the front side 40 of theauxiliary air foil 35. The lower partial stream 48 flows along thebottom side 31 of the air foil 29 and along the backside 39 of theauxiliary air foil 35. To the rear of the auxiliary air foil 35, the twopartial streams 47 and 48 recombine and flow together toward the upperend of the vehicle rear section, where they meet with the air flow 49flowing along the vehicle top side, with which they flow off togethertoward the rear as summation stream 50. Only a comparatively smallregion of detached flow 51 results thereby at the upper end of thevehicle rear section. The gap flow 52 through the through-flow gap 42between the rear end of the air foil 29 and the forward end of theauxiliary air foil 35 is of considerably significance for asubstantially detachment-free circumcirculation of the auxiliary airfoil 35, i.e., a circumcirculation exhibiting a small detachment. It isforcibly obtained by the above-described configuration and shape withinthe area of the through-flow gap 42.

The air flow effects a pressure distribution 53 along the bottom side 31of the air foil 29 and a pressure distribution 54 along the backside 39of the auxiliary air foil 35 as shown in FIG. 6. The vacuum values,which result with a predetermined in-flow that results at apredetermined vehicle velocity, are thereby shown as vectors along theair foil contours. A suction force S29, respectively, S35 will establishitself at the two air foils 29 and 35. The resulting suction force 29which is effective at the air foil 29 can be decomposed into a negativelift component -Z29 and into a propulsion component -X29. In acorresponding manner, the resulting suction force S35 which is effectiveat the auxiliary air foil 35, can be decomposed into a negative liftcomponent -Z35 and into a driving resistance component X35. The partialstreams 47 and 48, which exit obliquely upwardly and rearwardly, producereaction forces R47 and R48 which can also be decomposed intocorresponding components -Z and -X. The sum of all -Z-componentsproduces the aerodynamic lift, respectively, the aerodynamic negativelift.

In deviation from the illustrated embodiment, an air guide device may beprovided which, in lieu of two separate air foils, includes a single airguide device air foil that carries out the functions of the main airfoil and of the auxiliary after-air foil. Such an air guide device airfoil may also integrate the rear bumper. In lieu of the through-flow gap42, such an air guide device-air foil may be provided with through-flowopenings for a gap-flow which enhances the attachment of the lowerpartial flow along the outside of the air guide device-air foil.

According to FIG. 7, to assure a disturbance-free deflection of thelower partial stream 48, an auxiliary air foil 55 may be provided whichis arranged obliquely below and to the rear of the auxiliary after-airfoil 35 with a spacing from the latter. The auxiliary air foil 55 issecured by means of arms 56 at the auxiliary after-air foil 35 and withits concavely curved top side deflects the gap flow 52 which passesthrough the gap 42 between the air foil 29 and the auxiliary air foil35, upwardly and enhances by its curved overall configuration thedeflection of the lower partial stream 48 which flows partially alongthe concavely curved top side and partially along the convexly curvedbottom side of the auxiliary air foil 55. The air guide deviceconstituted by the air foil 29, the auxiliary after-air foil 35 and theauxiliary air foil 55 is thereby so arranged that the ground clearanceis at least as large as that of the forward area of the rear floor 17and additionally the boundary curb angle δ is kept open.

According to FIG. 8, a pre-air foil 57 is arranged ahead of the air foil29 which has the task to conduct to the air foil 29 undisturbedin-flow-air from the floor-near areas. The pre-air foil 57 is arrangedaltogether in the space between the two vehicle rear wheels 2. It is notnecessary within this space to maintain the curb clearance 58 with aheight of about 140 mm. to about 160 mm. which must be observed for theair guide device, i.e., especially for the air foil 29 to the rear ofthe rear vehicle wheels. Depending on the intended use conditions of thevehicle, a smaller ground clearance of about 80 mm. to about 120 mm. canbe accepted in the space between the vehicle rear wheels 2.

Deviating from the heretofore described embodiments in which the airguide device is in each case rigidly secured at the vehicle body wherebyalways a constant arrangement of the air foils relative to the rearfloor is assured, but different ground clearance distances may resultdepending on the downward spring strokes, provision may be madeaccording to the present invention that an air foil is retained at thevehicle body changeable in its position so that its ground clearance canbe kept far-reachingly constant independently of the downward springstrokes.

According to FIGS. 9 to 11, provision is made that an air foil 59 ispivotally secured in proximity of its rear end at the vehicle body bymeans of a pivot bearing 60. An adjusting mechanism 61 engages inproximity of the forward end of the air foil 59 which is pivotallyconnected with the rear axle transmission housing 62 but may also beconnected with another body part. In FIGS. 9 to 11, three differentpositions are illustrated which result at different loads of thevehicle. FIG. 9 illustrates the position which will establish itself ifonly one driver represents the load of the otherwise empty vehicle. Thevehicle body is far-reachingly lifted by the rear axle springs and therear axle transmission housing 62 has the maximum ground clearance 63 ofabout 200 mm. The adjusting mechanism 61 is extended so that a pre-airfoil 64 secured at the air foil 59 has a ground clearance C of about 120mm. within the space between the vehicle rear wheels 2. FIG. 10illustrates an intermediate position in which the vehicle carries amedium load, for example, in which a five-seater passenger motor vehicleis occupied by three persons. With this load, the rear axle transmissionhousing 62 only still has a medium ground clearance 65 of about 160 mm.The adjusting mechanism 61 is somewhat retracted so that the groundclearance C of the pre-air foil 64 is maintained unchanged. FIG. 11illustrates the condition with maximum permissive load of the vehicle.The rear axle transmission housing 62 only has still a minimum groundclearance 66 of about 120 mm. under this load condition. The adjustingmechanism 61 has effected a further pivoting of the air foil 59 togetherwith the pre-air foil 64 rigidly secured at the same so that also inthis load condition, the ground clearance C of the pre-air foil 64 ismaintained.

The pivotal adjustment of the air foil 59 can take place controlled asalso regulated in dependence on the static downward spring strokes.Additionally, the adjusting mechanism can be so constructed that dynamicheight changes, which additionally result during the drive, are takeninto consideration and the air foil 59, respectively, its pre-air foil64 always maintains far-reachingly the same ground clearance. Differingfrom the illustrated embodiment, the forward end of the air foil, inlieu of being connected with the vehicle body, may be connected with astructural part or component fixed with the wheel so that always aconstant predetermined ground clearance is maintained. Im lieu of apivot bearing, a translatory displacement of the air guide device mayalso be provided.

Owing to the adjustability of the air foil 59 together with the pre-airfoil 64, it is achieved in an advantageous manner that air is alwaysseized by the air guide device from areas as close to the floor aspossible, independently of the respective instantaneous height positionof the vehicle body, so that of the air flowing along underneath thevehicle, as large as possible a proportion reaches the space between theair guide device which is formed by the pre-air foil 64, the air foil 59and the after-air foil 35, and the rear floor 17. Additionally, theadjustability of the air foil 59 together with the pre air foil 64brings about that the overall configuration of the air guide deviceadapts itself in a favorable manner to the respective spacing of therear floor 17 from the road surface 7. Differing from the illustratedembodiment, the adjustment can also take place in such a manner that nota constant ground clearance of the pre-air foil 64, respectively, of theair foil 59 is maintained but instead the ground clearance of the airguide device also increases from a minimum value which exists at thelowest height position of the vehicle body, starting with increasingheight position of the vehicle body in dependence on the same, however,to a lesser extent than the height of the vehicle body, for example,changes proportional thereto.

According to FIGS. 12 and 13, an aerodynamically constructeddisplacement body 68 is provided at the bottom side of the vehicle bodyabove an air foil 69 within the space to the rear of the rear axletransmission housing 67; an after-air foil 70 is series-connected to therear of the air foil 69. It is achieved by the displacement body 68 thatdisturbances of the air flow which might be caused by the rear axletransmission housing 67 are far-reachingly avoided so that theeffectiveness of the air guide device is assured far-reachinglyundisturbed. The displacement body 68 may at the same time beconstructed as a component of the exhaust installation, for example, asrear-muffler, or may be constructed as component of a luggage space inwhich it may form a trough-shaped recess.

In the embodiment according to FIG. 14, turbulence generators 72 arearranged at an air foil 71, and more particularly at the bottom side 71aof the air foil 71 spaced approximately one-third of the length of theair foil 71 from the rear end of the air foil 71. In a correspondingmanner, an after-air foil 73, which is series-connected to the rear ofthe air foil 71, is provided at its backside 74 with turbulencegenerators 75, and more particularly slightly above the center of thebackside 74. Within the area of the detachment-endangered flow, supplyan energy-rich external flow to the wall-near flow. A flow detachment isprevented thereby or at least reduced.

FIGS. 15 to 19 illustrate some embodiments of such turbulencegenerators, so-called vortex generators. The in-flow direction isindicated in each case by an arrow V.

According to FIG. 15, small air-foil-shaped profiles 76 are providedsymmetrically to the flow direction and at a distance from one anotherwhich are disposed perpendicular on the convex circumcirculated air foilside and point away from the same.

According to FIG. 17, an approximately tetrahedrally shaped body 77 isprovided as vortex generator.

According to FIGS. 18 and 19, the circumcirculated air foil side isprovided with a recess 78 which extends in the flow direction, and inwhich small air foils 79 are arranged that effect a vortexing of theflow into the recessed bottom.

In the embodiment according to FIGS. 20 to 22, an air foil 80 isconstructed as part of the exhaust installation, namely, asrear-muffler. The silencing takes place in the middle part 81 of the airfoil 80, as viewed in the in-flow direction. Within this part of the airfoil 80, a forward muffler or silencing chamber 82, a middle muffler orsilencing chamber 83 and a rear muffler or silencing chamber 84 arearranged which extend each transversely to the in-flow directionapproximately over the entire length of the air foil 80, occupy theentire height of the center part 81 of the air foil 80 and adjoin oneanother. The forward part of the air foil 80, as viewed in the in-flowdirection, is constructed also aerodynamically as nose cap 85. The rearpart 86 of the air foil 80 is also constructed aerodynamically andserves at the same time as radiation protection covering. The exhaustend line 87 protrudes from the rear muffler chamber 84 through the rearpart 86 of the air foil 80 and terminates within the center area of theair foil 80 transverse to the in-flow direction with four exhaustopenings 88 in the rear edge of the air foil 80 which are arrangedsymmetrically to the center line 88 of the air foil 80 extending in thein-flow direction. The exhaust openings 88 each have a dimension in thevehicle transverse direction which is several times as large as theopening dimension in the vertical direction. The exhaust end line 87 isdirected with its exhaust openings 88 toward the lower area of thebackside 39 of the after-air foil 35 which is series-connected to therear of the air foil 80. The flow direction of the exhaust gases isindicated in FIG. 20 by an arrow 90.

It is achieved by this construction that the air foil 80 fulfillssimultaneously several functions so that a structural simplification ofthe vehicle results therefrom. Therebeyond, it is achieved that also theexhaust gases which are guided with high velocity along the vacuum sideof the auxiliary air foil 35 in contour-proximity, owing to which a veryhigh vacuum results at this place, contribute to the achievement ofnegative lift.

Differing from the embodiments described so far in which the respectiveair foil has a predetermined always constant cross section, an air foilgenerally designated by reference numeral 91 has in the embodimentaccording to FIGS. 23 and 24 a variable cross section. The air foil 91essentially consists of an air foil main body 92 and of an air foilshell 93. The air foil main body 92 forms with its top side essentiallythe top side (pressure side) and with its rear end the rear edge of theair foil 91. The air foil shell 93 forms essentially the bottom side(vacuum side) and the front edge of the air foil 91. The air foil shell93 is pivotally supported with its rear end at 94 in the rear area ofthe air foil main body 92 at the latter. The pivot bearing 94 enables tothe air foil shell 93 relative movements in the height direction withrespect to the air foil main body 92. In the operating position (FIG.23) the air foil shell 93 is lowered as far as possible. In thisposition, it is held against an abutment (not shown) by a spreadingspring 95 which is supported, on the one hand, at the forward end of theair foil main body 92 and, on the other, at the forward end of the airfoil shell 93. The free end of the air foil shell 93 is directedrearwardly, extends up to the forward end of the air foil main body 92except for a small distance and forms the forward end of the top side ofthe air foil 91.

In the operating position, the air foil shell 93 has as small aspossible a ground clearance 96 which is determined by regulations or bythe requirements of the practical driving operation. The air guide shell93 can be lifted from the operating position into the deflected endposition (FIG. 24) against the force of the spreading spring 95 up toabutment at the bottom side of the air foil main body 92. In thisposition, the air guide shell 93 has a ground clearance 97 which isconsiderably greater than the ground clearance 96 in the operatingposition. For example, the ground clearance 97 may be larger than theground clearance 96 by about 25%.

The arrangement of the movable air guide shell 93 makes it possible, onthe one hand, to provide an air foil with smallest possible groundclearance in the operating position which, by reason of the high in-flowvelocity and the high vacuum at the air foil bottom side, produces alarge negative lift action, and, on the other hand, when drivingbackwards, can drive with the vehicle rear section over relatively highobstacles, for example, a high curbstone, which deflects the air guideshell 93 in the upward direction without damaging the air guide device,as might be the case, for example, when parking in a reverse direction.

In the embodiment according to FIGS. 25 and 26, an air foil generallydesignated by reference numeral 98 with a changeable cross section isalso provided. An air foil main body 99 protrudes approximately with itsforward third into the space between the vehicle rear wheels 2. It formswith its top side the top side (pressure side) of the air foil 98, withits rear end, the rear edge of the air foil 98, with its forward end theforward edge of the air foil 98, and with the bottom side of its forwardpart 100, the forward part of the bottom side (vacuum side) of the airfoil 98. To the rear of the forward part 100, the air foil main body 99is not shaped corresponding to the aerodynamic requirements, but is keptflat. An air foil or air guide shell 101 is pivotally secured pivotal inthe vertical direction in the rear area of the air foil main body 99;the air guide shell 101 extends from the pivot bearing 102 forwardly upto the forward part 100 of the air foil main body 99. In its lowest endposition, the operating position, which is illustrated in FIG. 25, theforward end of the bottom side of the air guide shell 101 adjoins therear end of the bottom side of the forward part 100 of the air foil mainbody 99 and forms the rear part of the bottom side (vacuum side) of theair foil 98. Its forward end reaches slightly into the space between thevehicle rear wheels 2. It is kept in the operating position by aspreading spring 103 which is arranged in a pocket 104 of the air foilmain body 99; from the operating position it can be deflected upwardlyup to abutment at the air foil main body 99 against the force of thespreading spring 103. In the operating position in which the air guideshell 101 is in its lowest end position, the air guide shell 101 has aground clearance 105 which, taking into consideration the regulationsand the requirements of the practical driving operation, is as small aspossible in order to produce as large as possible a negative lift. Inthe deflected end position, in which the air guide or air foil shell 101is lifted against the force of the spreading spring 103 up to abutmentat the bottom side of the rear part of the air foil main body 99 (FIG.26), the air guide shell 101 has a ground clearance 106 which is largerby about one-fourth than the ground clearance 105 which the air guideshell 101 has in the operating position.

Also this embodiment enables as low as possible an arrangement of theair foil 98 for a favorable operating manner and nonetheless therearward parking at a relatively high obstruction, for example, at ahigh curbstone, with respect to which the air guide shell 101 deflectsyieldingly. The construction of the forward part of the air foil 98 ascomponent of the air foil main body 99 additionally assures a completelysatisfactory pressure build-up at the forward part of the air foil 98which, by reason of its arrangement between the vehicle rear wheels 2can remain in its low position also during the rearward parking at highobstacles.

In order to achieve a good efficiency over the entire width of the airfoil and of the auxiliary air foil, air guide walls (not shown) may beprovided at the air foil ends or in their proximity at the vehicle sideswhich extend in the vehicle longitudinal direction. They may be fastenedboth at the vehicle body as also at the air foil ends.

While we have shown and described several embodiments in accordance withthe present invention, it is understood that the same is not limitedthereto but is susceptible of numerous changes and modifications asknown to those skilled in the art, and we therefore do not wish to belimited to the details shown and described herein but intend to coverall such changes and modifications as are encompassed by the scope ofthe appended claims.

We claim:
 1. A motor vehicle, especially a passenger motor vehicle, witha rear axle and with vehicle floor means including rear floor means, inwhich for achieving a good grip of the vehicle the vehicle floor meansis constructed in its rear area essentially smooth-surfaced and risingtoward the vehicle end, air foil means arranged in the space underneaththe rising rear floor means at which a negative lift becomes effectiveduring air in-flow from the vehicle front section, the forward end ofthe rising rear floor means being arranged at least within the area ofthe vehicle rear axle, the rising rear floor means forming the top sideof a rear diffusor means whose bottom side is formed by the roadsurface, and at the vehicle end having a considerable spacing from theroad surface, the air foil means being so arranged that it protrudeswith its forward end into the space between the vehicle rear wheels andits bottom side has at least the same distance from the road surface asthe vehicle floor means at its lowest place in the vehicle areas locatedin front of the vehicle rear section.
 2. A motor vehicle according toclaim 1, wherein the air foil means protrudes approximately with itsforward third into the space between the vehicle rear wheels.
 3. A motorvehicle according to claim 1, wherein the forward end of the rising rearfloor means is arranged at least approximately within the area in frontof a rear axle suspension.
 4. A motor vehicle according to claim 1,wherein the transition from the area of the vehicle floor means arrangedin front of the rising rear floor means to the rising rear floor meanstakes place gradually and is constructed rounded-off.
 5. A motor vehicleaccording to claim 1, wherein the vehicle floor means is constructedfar-reachingly smooth-surfaced within the area in front of the risingrear floor means.
 6. A motor vehicle according to claim 1, wherein therising rear floor means has at least in the center area between theforward and rear adjoining areas thereof an essentially constant slopeand the angle of inclination subtended by the rear floor means risingfrom the center area and the horizontal amounts to about 10° to about40°.
 7. A motor vehicle according to claim 6, wherein the angle ofinclination amounts to about 25°.
 8. A motor vehicle according to claim6, wherein the rising rear floor means has in the rear area a graduallyincreasing slope toward the rear end of the rising rear floor means andan angle of inclination at the rear end with respect to the horizontalof about 40° to about 90°.
 9. A motor vehicle according to claim 8,wherein the last-mentioned angle of inclination is about 70°.
 10. Amotor vehicle according to claim 1, wherein the rear end of the risingrear floor means adjoins an essentially at least approximatelyvertically arranged rear closure wall of the vehicle.
 11. A motorvehicle according to claim 10, wherein a detachment edge is provided atthe rear end of the rising rear floor means.
 12. A motor vehicleaccording to claim 1, wherein the air foil means is arranged essentiallyflat.
 13. A motor vehicle according to claim 1, wherein an auxiliary airfoil means is connected in series to the rear of and at a distance fromthe air foil means, a negative lift force being also effective at theauxiliary air foil means during an air in-flow coming from the vehiclefront section.
 14. A motor vehicle according to claim 13, with a rearbumper means, wherein the auxiliary air foil means forms a structuralunit together with the rear bumper means.
 15. A motor vehicle accordingto claim 14, wherein the rear bumper means is integrated into theauxiliary air foil means.
 16. A motor vehicle according to claim 13,wherein the first-mentioned air foil means is coordinated approximatelyto the rear half of the center area of the rising rear floor means andthe auxiliary air foil means is coordinated to the rear area of therising rear floor means.
 17. A motor vehicle according to claim 13,wherein the first-mentioned air foil means is arranged essentially flatand the auxiliary air foil means essentially steep.
 18. A motor vehicleaccording to claim 13, wherein the rear end of the first-mentioned airfoil means is arranged underneath the forward end of the auxiliary airfoil means.
 19. A motor vehicle according to claim 18, wherein athrough-flow gap is provided between the rear end of the first-mentionedair foil means and the forward end of the auxiliary air foil means whichhas a gap width of about 10 to about 60 mm.
 20. A motor vehicleaccording to claim 13, wherein the distance of the air guide deviceformed by the first-mentioned air foil means and the auxiliary air foilmeans from the rising rear floor means becomes initially larger from infront toward the rear and becomes smaller again in the rear area.
 21. Amotor vehicle according to claim 20, wherein the distance of the forwardend of the first-mentioned air foil means from the rising rear floormeans becomes approximately as large as or larger than the distance ofthe rear end of the auxiliary air foil means from the rear end of therising rear floor means.
 22. A motor vehicle according to claim 13,wherein the interior width between the rear end of the auxiliary airfoil means and the rising rear floor means amounts to about 30 mm. toabout 200 mm.
 23. A motor vehicle according to claim 13, wherein therear area of the auxiliary air foil means forms together with the reararea of the rising rear floor means a line with a cross sectionremaining substantially constant for over its length or a nozzle with anessentially upwardly and slightly rearwardly directed exit flowdirection.
 24. A motor vehicle according to claim 13, wherein the reararea of the auxiliary air foil means subtends with the horizontal anangle of about 50° to about 90°.
 25. A motor vehicle according to claim13, characterized in that the rear area of the auxiliary air foil meanshas only a slight tapering and terminates essentially blunt.
 26. A motorvehicle according to claim 25, wherein the rear area of the auxiliaryair foil means has a thickness of about 10 mm. to about 60 mm.
 27. Amotor vehicle according to claim 13, wherein a further auxiliary airfoil means is arranged to the rear of the through-flow gap presentbetween the rear end of the first-mentioned air foil means and theforward end of the first-mentioned auxiliary air foil means.
 28. A motorvehicle according to claim 13, wherein a pre-air foil means iscoordinated to the first-mentioned air foil means, said pre-air foilmeans being arranged inside of the envelope curve of the vehicle rearwheels and its bottom side having a smaller distance from the roadsurface than the bottom side of the first-mentioned air foil means. 29.A motor vehicle according to claim 28, wherein the first-mentioned airfoil means is supported adjustable in the vertical direction at a fixedvehicle part.
 30. A motor vehicle according to claim 29, wherein thesupport includes a pivotal connection.
 31. A motor vehicle according toclaim 30, wherein the pivotal connection is provided within the reararea of the first-mentioned air foil means.
 32. A motor vehicleaccording to claim 29, further comprising an air foil height-adjustingmeans.
 33. A motor vehicle according to claim 32, wherein the air foilheight-adjusting means is operable automatically in dependence on theheight position of the vehicle body.
 34. A motor vehicle according toclaim 29, wherein the first-mentioned air foil means is operativelyconnected for purposes of adjustment with at least one of the supportsof the vehicle rear wheels.
 35. A motor vehicle according to claim 13,wherein at least one of the first-mentioned air foil means and theauxiliary air foil means includes vortex generator means on the vacuumside thereof.
 36. A motor vehicle according to claim 1, wherein the airfoil means is constructed as muffler.
 37. A motor vehicle according toclaim 36, wherein said muffler is a rear muffler.
 38. A motor vehicleaccording to claim 36, wherein the muffler includes damping chambermeans arranged in a center part of the air foil means as viewed in thein-flow direction.
 39. A motor vehicle according to claim 36, whereinthe rear part of the air foil means is constructed as radiationprotection covering.
 40. A motor vehicle with an exhaust end lineaccording to claim 36, wherein the outflow end of the exhaust end lineis arranged in the rear edge of the air foil means.
 41. A motor vehicleaccording to claim 40, wherein an auxiliary air foil means is connectedin series to the rear of and at a distance from the air foil means, anegative lift force being also effective at the auxiliary air foil meansduring an air in-flow coming from the vehicle front section.
 42. A motorvehicle according to claim 41, wherein the exhaust end line is directedtoward the forward area of the vacuum side of the auxiliary air foilmeans.
 43. A motor vehicle according to claim 1, wherein the air foilmeans has a variable cross section.
 44. A motor vehicle according toclaim 43, wherein the bottom side of the air foil means is constructedat least in part as air guide shell means which is pivotally securedwith its rear end about a substantially horizontal axis at the rear endof an air foil main body which, as to the rest, forms the air foilmeans, between a lower end position and an upper end position.
 45. Amotor vehicle according to claim 44, wherein at least one spreadingspring means is provided between the air foil main bodY and the airguide shell means.
 46. A motor vehicle according to claim 44, whereinthe air guide shell means protrudes beyond the forward end of the airfoil main body.
 47. A motor vehicle according to claim 44, wherein theair guide shell means extends essentially only over the part of the airfoil main body which is arranged outside of the envelope curve of thevehicle rear wheels, and in its lower end position adjoins the bottomside of the forward part of the air foil main body arranged between thevehicle rear wheels.
 48. A motor vehicle according to claim 1, whereinair guide walls are provided at the vehicle sides within the rear areawhich extend essentially in the vehicle longitudinal direction.
 49. Amotor vehicle according to claim 48, wherein the air guide walls extendfrom the vehicle body downwardly to approximately at the height of theair foil means.
 50. A motor vehicle according to claim 49, wherein theair guide walls are arranged at the ends of the air foil means.
 51. Amotor vehicle according to claim 13, wherein the air guide walls extendfrom the vehicle body downwardly to approximately at the height of theair foil means and the auxiliary air foil means.
 52. A motor vehicleaccording to claim 51, wherein the air guide walls are arranged at theends of the air foil means and of the auxiliary air foil means.